<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="./vue.js"></script>
    <title>Document</title>
    
</head>
<body>
    <div id="app">
        <input type="text" v-model="n1">
        <select v-model="opt">
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>
        </select>
        <input type="text" v-model="n2">
        <input type="button" value="="@click="calc">
        <input type="text" v-model="result">

    </div>
</body>
<script>
var vm=new Vue({
    el:'#app',
    data:{
        n1:0,
        n2:0,
        result:0,
        opt:'+'
    },
    methods:{
        calc(){
            switch(this.opt){
                case '+':
                this.result=parseInt(this.n1)+parseInt(this.n2)
                break;
                case '-':
                this.result=parseInt(this.n1)-parseInt(this.n2)
                break;
                case '*':
                this.result=parseInt(this.n1)*parseInt(this.n2)
                break;
                case '/':
                this.result=parseInt(this.n1)/parseInt(this.n2)
                break;
            }
        }
    }
});
</script>
</html>